PAF Grant Maclean

PAF Awards $50,000 New Research Grant

Ken Maclean, PhD, University of Colorado Denver 

“Chemical Chaperone Treatment to Restore Enzyme Activity in Folding Mutations of Propionyl-Co-A Carboxylase: Towards a Personalized Therapeutic Strategy in Propionic Acidemia (PA)” – In Summer 2020, PAF awarded a $50,000 grant.”  

Propionic acidemia (PA) is a severe life-threatening disease for which there is currently no truly effective treatment. The disease is caused by mutation in one of the two genes that code for the enzyme propionyl-CoA carboxylase (PCC). This enzyme is made up of two different proteins that fold around each other into a complex structure with six of each of these two molecules. This is a very unusual and complex structure for a metabolic enzyme and recent work in our laboratory has found that a number of specific mutations that cause PA cause problems by interfering with the protein folding and/or assembly process leading to a non-functional enzyme and thus the disease. In cells, proteins with complicated folding patterns are often assisted in their folding by other proteins called chaperones. We have observed that a number of mutant forms of PCC can be restored to normal activity if they are helped to fold correctly using these chaperone proteins. In our study, we will examine a number of chemicals that can also function as chaperones and assist with protein folding with a view towards restoring full activity in mutant forms of PCC. This work will initially occur in a bacterial PCC expression system to identify promising compounds and then depending upon progress, move into treating human PCC patient derived cells. These studies have the potential to serve as an initial first step in the rational design of a personalized medicine strategy for patients with specific mutations causing PA.

PAF research summary Elango

PAF Awards $44,253 New Research Grant

Rajavel Elango, PhD, University of British Columbia

“Optimizing amino acids in medical foods to manage propionic acidemia”  

Propionic Acidemia (PA) is primarily caused by an enzymatic defect, propionyl-CoA carboxylase (PCC), in the catabolic pathway of valine, isoleucine and other propiogenic precursors. The dietary management of PA mainly depends on protein restriction from food to reduce supply of propiogenic amino acids, and the use of special medical foods. These medical foods contain all essential amino acids and nutrients, but no propiogenic compounds. Recently, concerns have been raised about their use, due to the imbalanced content of the Branched Chain Amino Acids (BCAA) – high leucine, to minimal or no valine and isoleucine. The imbalanced mixture of BCAA negatively impacts plasma concentrations of valine and isoleucine, and has been proposed to affect growth in pediatric PA patients. 

In an ongoing retrospective natural history study (n=4), patients with PA treated at our center from birth (or diagnosis) to age 18y, we observed that higher intake of medical food (compared to intact protein) results in lower ht-for-age Z scores. Based on these pilot data, we propose that there is an immediate need to determine the optimal amounts of leucine to be present in the medical foods.

Therefore, the specific objectives of the current study are to:

  1. Stable isotope studies
    1. Determine the ideal ratio among BCAA in children using the stable isotope-based indicator amino acid method to optimize protein synthesis in a Proof-of-Principle approach.
    2. Test the ratio among BCAA using the same stable isotope-based method in our cohort of PA patients to determine impact on protein synthesis, and plasma metabolite responses.
  2. Determine the impact of the use of natural (intact) vs formula (medical food) protein on anthropometric, biochemical and clinical outcomes via a retrospective natural history study of PA patients treated at BC Children’s Hospital.

Recent dietary guidelines for PA are discouraging the reliance on medical foods as a sole dietary source. However most individuals with PA are at risk for malnutrition and depend on these medical foods as an easy tolerable source of energy and protein. Thus, determining the optimal ratio of BCAA in PA medical foods is necessary to optimize protein synthesis, promote anabolism, growth and prevent the accumulation of toxic metabolites. 

Our laboratory, equipped with use of novel stable isotope tracers to examine protein and amino acid metabolism, is ideally suited to address the question of the ideal BCAA ratio to be used for dietary management of PA and potentially impact health outcomes.

 

The Propionic Acidemia Nutrition Guidelines are now published

Great News – The “Propionic Acidemia Nutrition Guidelines” Are Now Published!

The Nutrition Guideline Committee is happy to announce that the Organic Acidemia Workgroup has published the “Propionic Acidemia (PROP) Nutrition Guidelines” in the February, 2019 issue of Molecular Genetics and Metabolism. The article is available and can be downloaded at no cost at https://doi.org/10.1016/j.ymgme.2019.02.007.

Publication of the PROP/PA Nutrition Guidelines in Molecular Genetics and Metabolism brings the latest evidence- and consensus-based nutrition management recommendations to the attention of clinicians, researchers, policy makers, insurers, and patients.

The new Nutrition Management Guidelines for PROP/PA provide:

  • New directions including:
    • A greater emphasis on nutritional needs such as nutrient intake, nutritional interventions, supplementation, etc.
    • Less emphasis on  medical management which has been covered in previous publications;
    • Additional topics such as monitoring to ensure nutritional adequacy, nutritional issues with pregnancy and lactation, nutritional management for secondary complications such as pancreatitis, and finally a section addressing liver transplantation and the nutritional management before, during, and after the procedure.

 

Two consumer-oriented pieces, Frequently Asked Questions and a Consumer Summary, provide patients and families with information to use when interacting with their providers. The summary highlights key recommendations and suggests questions that patients and families may want to discuss with the metabolic team.

  • When patients and health care providers (HCPs) have the same information, they can work together as a team to identify the treatment that is best for the patient’s situation.
  • You can access these pieces at the Genetic Metabolic Dietitians International (GMDI) or Southeast Genetics Network websites located at http://www.Southeastgeneticsnetwork.org/ngp  and http://www.GMDI.org
  • The new guidelines should lead to greater consistency of care across centers.
    • There are several important resources included in the guidelines including recommended nutrient intakes, monitoring schedules, and nutritional interventions tables.
    • A web site that provides all the resources and references used to develop the guidelines is available so that health care clinicians and others can readily obtain the background information related to the guidelines at the websites listed above.
    • The guidelines development method utilized evidence from published research, practice-based medical literature and expert consensus processes.

Propionic Acidemia Foundation Research Grant – Richard

PAF Awards $33.082.12  Research Grant in 2019

PAF Awards $30,591  Continuation Grant in 2020

Eva Richard, PhD, Universidad Autonoma de Madrid, Spain

“Cardiomyocytes derived from induced pluripotent stem cells as a new model for therapy development in propionic acidemia”

Understanding the cellular and molecular mechanisms that occur in genetic diseases is essential for the investigation of new strategies for their prevention and treatment. In this context, induced pluripotent stem cells (iPSC) offer unprecedented opportunities for modeling human disease. One of the fundamental powers of iPSC technology lies in the competency of these cells to be directed to become any cell type in the body, thus allowing researchers to examine disease mechanisms and identify and test novel therapeutics in relevant cell types.

The main objective of this project is focused on the generation of human iPSC-derived cardiomyocytes (hiPSC-CMs) from propionic acidemia (PA) patients as a new human cellular model for the disease.In PA, cardiac symptoms, namely cardiac dysfunction and arrhythmias, have been recognized as progressive late-onset complications resulting in one of the major causes of disease mortality. Using hiPSC-CMs we will study cellular processes, such as mitochondrial function and oxidative stress which have been recognized as main contributors for PA pathophysiology. In addition, our aim is to unravel novel altered pathways using high-throughput techniques such as RNAseq and miRNA analysis. We will also examine the potential beneficial effects of an antioxidant and a mitochondrial biogenesis activator in PA cardiomyocytes. The results that derive from this project will be relevant for the disease providing insight into the affected biological processes, and thus providing tools and models for the identification of novel adjuvant treatments for PA.

Update September 2019 – Eva Richard PhD

There is an unmet clinical need to develop effective therapies for propionic acidemia (PA). Advances in supportive treatment based on dietary restriction and carnitine supplementation have allowed patients to live beyond the neonatal period. However, the overall outcome remains poor in most patients, who suffer from numerous complications related to disease progression, among them cardiac alterations, a major cause of PA morbidity and mortality. In our research, we developed a new cellular model of PA based on induced pluripotent stem cells (iPSC) with the goal of defining new molecular pathways involved in the pathophysiology of PA which would be potential treatment targeting.

Traditionally, disease pathophysiology has been studied in immortalized or human cell lines and in animal models. Unfortunately, immortalizedcells often do not respond as primary cells and animal models do not exactly recapitulate patients‘ symptoms. So far, patients-derived fibroblasts have been mainly usedas cellular models in PAdue to theiravailability and robustness, but they have important limitations.

The ability to reprogram somatic cells to iPSCs has revolutionized the way of modeling human disease. To study rare diseases, stem cell models carrying patient-specific mutations have become highly important as all cell types can be differentiated from iPSCs. We have generated and characterized two iPSC lines from patients-derived fibroblasts with defects in PCCA and PCCB genes. These iPSC lines can be differentiated into cardiomyocytes that mimic the tissue-specific hallmarks of the disease. The presence of PA cardiomyocytes has been easily established by visual observation of spontaneously contracting regions, and the expression of several cardiac markers. We have observed that PCCA-deficient cardiomyocytes present an increase in degradation products and in lipid droplets, and exhibit mitochondrial dysfunction compared to control cells. We further discovered the down-regulation of several miRNAs in PCCA cardiomyocytes compared to control ones, and several miRNAs targets are currently being analyzed in order to investigate underlying cellular pathological mechanisms. Interestingly, we have performed several experiments to analyze the effect of the mitochondrial biogenesis activator, MIN-102 compound (PPAR agonist, derivative of pioglitazone) in cardiomyocytes.

Preliminary results showed an increase in the oxygen consumption rateof PCCA and control cells. In our next steps, we plan to complete the analysis in the PCCA cardiomyocyte line, characterize PCCB cardiomyocytes and to study in depth the therapeutic potential of MitoQ and MIN-102 compounds.

We would like to sincerely thank the Propionic Acidemia Foundation for supporting our research.

Update March 2020

 “Cardiomyocytes derived from induced pluripotent stem cells as a new model for therapy development in propionic acidemia.”

Eva Richard, Associate Professor

There is an unmet clinical need to develop effective therapies for propionic acidemia (PA). Advances in supportive treatment based on dietary restriction and carnitine supplementation have allowed patients to live beyond the neonatal period. However, the overall outcome remains poor in most patients, who suffer from numerous complications related to disease progression, among them cardiac alterations, a major cause of PA morbidity and mortality. In our research, we developed a new cellular model of PA based on induced pluripotent stem cells (iPSC) with the goal of defining new molecular pathways involved in the pathophysiology of PA which could be potential therapeutical targets.

Traditionally, disease pathophysiology has been studied in immortalized or human cell lines and in animal models. Unfortunately, immortalized cells often do not respond as primary cells and animal models do not exactly recapitulate patients‘ symptoms. So far, patients-derived fibroblasts have been mainly used as cellular models in PA due to their availability and robustness, but they have important limitations.

The ability to reprogram somatic cells to iPSCs has revolutionized the way of modeling human disease. To study rare diseases, stem cell models carrying patient-specific mutations have become highly important as all cell types can be differentiated from iPSCs. We have generated and characterized two iPSC lines from patients-derived fibroblasts with defects in the PCCA and PCCB genes. These iPSC lines can be differentiated into cardiomyocytes that mimic the tissue-specific hallmarks of the disease. The presence of cardiomyocytes has been easily established by visual observation of spontaneously contracting regions, and the expression of several cardiac markers. PCCA iPSC-derived cardiomyocytes exhibited an alteration of autophagy process with an accumulation of residual bodies and mitochondrial dysfunction characterized by reduced oxygen consumption and alteration of mitochondrial biogenesis due to a deregulation of PPARGC1A. We also evaluated the expression of heart-enriched miRNAs previously associated with cardiac dysfunction and several miRNAs were found deregulated. Furthermore, we found increased protein levels of Herp, Grp78, Grp75, sigma-1R and Mfn2 suggesting ER stress and calcium perturbations in these cells.

We are planning to analyze PCCB cardiomyocytes to compare the results with PCCA and control data. We are working to obtain mature cardiomyocytes in order to perform electrophysiology studies (K+ currents) using a whole-cell patch clamp method. We are interested in the study of the tissue-specific bioenergetic signature comparing cardiomyocytes derived from control and PA patients´ iPSCs by reverse phase protein microarrays (RPPMA). Future work also includes testing the effect of the mitochondrial biogenesis activator, MIN-102 compound (PPAR agonist, derivative of pioglitazone) and of the mitochondrial targeting antioxidant MitoQ in PA cardiomyocytes.

We would like to sincerely thank the Propionic Acidemia Foundation for supporting our research.

 

 

 

Propionic Acidemia Foundation Research Grant Guofang Zhang

PAF Awards $48,500 Research Grant

Guofang Zhang, PhD, Duke University

“Propionyl-CoA and propionylcarnitine mediate cardiac complications in patients with propionic acidemia”

Energy production is the central cardiac metabolism for continuous mechanical work. An average human adult heart consumes ~ 6 kg ATP/day. ATP storage in the heart is only sufficient to sustain the heart beat for a few seconds. A tightly coupled cardiac energy metabolism from various substrates is critical for sufficient ATP production required by normal heart function.

One molecule of palmitic acid (fatty acid) generates much more ATP than one molecule of glucose does after their complete metabolism.Fatty acids contribute ~70-90% cardiac energy production in normal condition. However, heart still maintains high flexibility of fuel switch in response to various available substrates. Acetyl-CoA is the first convergent metabolite derived from the diverse fuel substrates via different pathways and enters tricarboxylic acid cycle (TCAC) for energy production. Therefore, the level of acetyl-CoA or the ratio of acetyl-CoA/CoA tightly controls the metabolic fluxes from two major fuels, i.e.,glucose and fatty acid, in the heart. Acetyl-CoA or CoA level is also finely tuned by carnitine acetyltransferase (CrAT) that catalyzes the reversible interconversion between short-chain acyl-CoAs and acylcarnitines.Acetylcarnitine level is ~10-100 fold greater than that of acetyl-CoA in heart and is seen as the buffer of acetyl-CoA. CrAT is highly expressed in high energy demanding organs including heart and mediates fatty acid and glucose metabolism possibly by dynamically interconverting acetyl-CoA and acetylcarnitine into each other.The deficiency of CrAT has been shown to change cardiac fuel selection.

Propionic acidemia (PA) is often associated with cardiac complications. However, the pathological mechanism remains unknown. We have demonstrated that high exogenous propionate led to the propionyl-CoA accumulation and cardiac fuel switch from fatty acid to glucose in the perfused normal rat hearts (Am. J Physiol. Endocrinol. Metab.,2018,315:E622-E633). The deficiency of propionyl-CoA carboxylase in PA also induces the accumulation of propionyl-CoA. Next, we will attempt to understand whether and how the elevated propionyl-CoA in the Pcca-/- heart (collaboration with Dr. Michael Barry)could interrupt cardiac energy metabolism by investigating the fuel switch flexibility, CrAT mediated metabolism, and buffer capacity of acetylcarnitine using stable isotope-based metabolic flux analysis (J. Biol. Chem., 2015,290:8121-32). We hope that the outcome of this project will provide meaningful therapeutic recommendation for patients with PA, especially with the cardiac complication.

Liver Transplantation Part 2

Liver Transplantation

Part 2: Outcomes Following Liver Transplantation in Children with PA and MMA

James Squires, MD, MS

Dr. Squires is a liver disease specialist at UPMC Children’s Hospital of Pittsburgh and an assistant professor of pediatrics at the University of Pittsburgh School of Medicine.

Jodie M. Vento, MGC, LCGC

Jodie Vento is a genetic counselor and manager of the Center for Rare Disease Therapy at UPMC Children’s Hospital of Pittsburgh.

Part 1 of this article, published in the Spring 2018 issue, provided answers to questions that families may have about what to expect from a liver transplant for a child with Propionic Acidemia (PA). Here, in Part 2, the authors summarize and explain the findings of a recent study of outcomes in children with PA and methylmalonic acidemia (MMA) who received liver transplants at UPMC Children’s Hospital of Pittsburgh.

Why did you do this study?

Before we get to why we did this study, please allow us to back up a bit and briefly discuss the history of liver transplantation for PA and MMA, which was first proposed in the early 1990s. Because the enzyme deficiencies that cause PA and MMA exist throughout the body, not just in the liver, liver transplantation was never expected to be a cure for these diseases. The thinking was that by providing enough functional enzyme to minimize, if not eliminate, metabolic crises­––the most severe complications of PA and MMA for affected children, as well as one of the most frightening features of these diseases for families––a liver transplant could enhance stability and improve quality of life for affected children.

In recent years, policies on the allocation of donor livers in the United States have changed to give priority to patients with PA and MMA because of their risk of sudden, life-threatening metabolic crises. As a result, children with these disorders can now be listed for a liver transplant based on their diagnosis alone rather than on disease complications or severity.

A recent study, based on statistical analysis,found that liver transplantation for PA and MMA may increase both the length and quality of patients’ lives and decrease health care costs over a patient’s lifetime. However, because PA and MMA are rare disorders, it has been difficult to gather a strong body of evidence showing how well patients fare after undergoing a liver transplant.

The Pediatric Liver Transplant Program at UPMC Children’s Hospital of Pittsburgh was established in 1981 by world-renowned transplant surgeon Thomas E. Starzl, MD, PhD. Our Director of Pediatric Transplantation, George Mazariegos, MD, FACS, pioneered liver transplantation for children with metabolic diseases in 2004. Since then, UPMC Children’s has performed more than 330 liver transplants for children with metabolic diseases, more than any other transplant center. We’ve also performed more liver transplants in children than any other center in the United States and more living-donor transplants than any other pediatric center in the country. Our one-year survival rate for pediatric liver transplant patients is 98%, exceeding the national average of 95%, according to the Scientific Registry of Transplant Recipients (January 2018 release).

We decided to do this study because, given the breadth and depth of our experience in this field, we thought that we could make a useful contribution to medical knowledge by gathering and evaluating all of the information available to us on outcomes for all of the patients who have undergone a liver transplant for PA or MMA at our institution.

How did you do this study?

We searched our medical records database to identify all patients with a diagnosis of either PA or MMA who received either a liver transplant or a combined liver and kidney transplant between 2006 and 2017.To comply with patient privacy regulations, we first removed any and all information that could personally identify these patients. Then we examined data from their medical records and recorded information such as their age and family history, medical treatment received prior to the liver transplant, laboratory tests performed, and how they fared both immediately after the transplant and in the following months and years.

What did the study find?

We identified a total of nine patients with PA (three patients) or MMA (6 patients) who had undergone a liver or liver and kidney transplant at UPMC Children’s between 2006 and 2017. The age at which patients received their transplant ranged from one year old to 21 years old; the median, or midpoint, was nine years old. Five patients were female and four male. Eight of the nine patients had been diagnosed during their first week of life; one patient was diagnosed at age eight months.

Prior to the transplant, all of the patients had been treated with protein restriction and carnitine supplementation. Several were also receiving medication to reduce ammonia levels in the blood. Eight of the nine patients were being fed by a gastrostomy tube (also known as a “G-tube”). All were experiencing frequent metabolic crises that often required hospitalization. Additional disease-related complications included cardiomyopathy (damaged heart muscle), metabolic stroke, pancreatitis, and low blood cell counts.

Five of the six patients with MMA received combined liver and kidney transplants. One patient with MMA and all three patients with PA underwent liver transplants only. Patients’ median post-transplant length of stay in intensive care was just short of 30 days, while the total transplant-related hospital stay averaged 55 days. Patients were followed after their transplant for a median of 3.5 years (range one year to more than 11 years).

Six of the nine patients developed symptoms of liver rejection; one patient developed symptoms of kidney rejection. Rejection episodes were treated with steroids and higher doses of anti-rejection medication to suppress the immune system. None of the nine patients experienced transplant failure.

Two patients needed treatment for blood clots in the main artery that carries blood to the liver. A third patient needed treatment for a blockage in a vein that transports blood from the liver back to the heart.

Four patients experienced a build-up of bile in the liver that was caused by a blocked bile duct and required treatment with a biliary catheter. At the last follow-up, three of the four patients had been able to discontinue use of the biliary catheter.

Five patients developed viral infections that required treatment. No patients experienced a complication known as post-transplant lymphoproliferative disorder, a dangerous rapid increase in white blood cells that can sometimes occur in people who are taking medication to prevent rejection of a transplanted organ.

No patients have experienced metabolic crises since the transplant. All nine patients showed improved metabolic control––indicated by normal levels of lactic acid in the blood––during the first month after the transplant. Kidney function stabilized or improved in all patients with MMA. At the two-year post-transplant assessment, heart function had improved in a patient with PA and severe cardiomyopathy.

What conclusions can be drawn from the study’s findings?

In this study of nine children with PA or MMA who were followed for an average of 3.5 years, we show 100 percent survival for both patients and their transplanted organs.

For MMA, these findings are similar to those of other recently published reports. For PA, although our population is relatively small (three patients), our finding of 100 percent survival for both patients and transplanted organs stands in contrast to other published reports that found poor survival among patients with PA following a liver transplant.

Still, many patients experienced complications in the period immediately before, during, and after the transplant. The high rate of complications underscores the complexity of these metabolic diseases. The most common complications were those involving the blood vessels, including blood clotting in the main artery of the liver. This complication has been previously reported.

All patients had reduced levels of lactic acid in the blood, indicating improved metabolic control, both shortly after the transplant and at later postoperative follow-up. Complications such as kidney disease (in patients with MMA) and cardiomyopathy (in patients with PA) stabilized and improved after transplantation.

The fact that no patients experienced metabolic crises after transplantation indicates that partial enzyme replacement via a liver transplant enabled a “resetting” of patients’ metabolic fitness.

At UPMC Children’s our approach to nutritional support after a liver transplant has been to gradually ease protein restriction, with the goal of establishing a long-term individualized level of support for each patient. It is unlikely that protein restriction can ever be completely eliminated. However, the results of this study show that––with close monitoring by an experienced interdisciplinary team––protein restriction can safely be relaxed, in an individualized fashion, after a liver transplant.

What do the study results mean for children with PA and their families?

A liver transplant cannot cure PA. It can, however, reduce or eliminate metabolic crises and result in greater stability and better quality of life for children with PA. The decision as to whether a liver transplant is right for your child with PA is one that every family must make for themselves, based on their knowledge of their child and in consultation with a multidisciplinary team of experts who specialize in liver transplantation for metabolic diseases.

This study adds to the increasing body of evidence that liver transplantation can be performed safely and successfully in patients with severe, complex metabolic conditions such as PA and MMA, especially when performed at centers with broad and deep experience in the management of these highly challenging conditions.

Reference: Critelli K, McKiernan P, Vockley J, Mazariegos G, Squires RH, Soltys K, Squires JE. Liver Transplantation for Propionic Acidemia and Methylmalonic Acidemia: Peri-operative Management and Clinical Outcomes. In press, Liver Transplantation. Accepted for publication June 2018.

PAF Awards grant for Dr. Oleg Shchelochkov and Dr. Charles P. Venditti for $32,912

PAF awarded a  $32,912 research grant to Oleg Shchelochkov, M.D. and Charles P. Venditti MD, PhD at National Human Genome Research Institute, National Institutes of Health  – 2018

“Diversion of Isoleucine and Valine Oxidative Pathway to Reduce the Propionogenic Load in Propionic Acidemia.”

Patients with propionic acidemia require lifelong protein restriction. In addition to taking a protein restricted diet, many propionic acidemia patients are also prescribed medical formulas. This dietary approach aims to decrease the intake of four amino acids that can become propionic acid. These four amino acids – isoleucine, valine, threonine, and methionine – are called essential, because they cannot be made in the human body and need to be supplied from foods. Too much protein intake creates a situation where excess can lead to a buildup of propionic acid in the body. On the other hand, limiting these four amino acids too much can lead to poor growth. Therefore, patients’ diets are optimized to minimize propionic acid production while encouraging good growth. We wonder whether it is possible to increase dietary protein intake while minimizing the risk of propionic acid buildup.

To answer this question, we are planning to do a series of experiments in zebrafish. Why use zebrafish? Zebrafish share significant similarity to humans in how they process propionic acid. In addition, zebrafish reproduce and mature quickly, which are very important qualities to help search for new drugs that could be used to treat propionic acidemia. Our zebrafish are kept in a special building where the animals are being cared for by a dedicated team that includes scientists, veterinarians, engineers, aquatic specialists, and many others. They check on fish and feed them several times a day, maintain fish tanks, and keep their water very clean.

This type of facility is unique and had enabled our studies of metabolic diseases in zebrafish. Our ongoing studies have shown that zebrafish affected by metabolic diseases have symptoms that are very similar to patients. Even with treatment, affected fish have difficulty growing, get tired easily, have poor appetites and sometimes perish before adulthood. Using special genomic tools, we are planning to change in how the fish processes protein to direct it away from becoming propionic acid. As we make these changes to the biochemical pathways of propionic acidemia zebrafish, we will be carefully watching how these treatments improve their growth, development, appetite and survival. These experiments will help us understand how we can potentially reduce propionic acid toxicity while helping patients achieve a less restrictive diet.

Interview with Joel Pardo  – Summer  2020

Can you tell me about yourself and how you became interested in science?

I was always interested in the sciences. I think ultimately what propelled me towards a career in science was my research experience at the University of California, San Diego. The mentorship I received from Dr. Joshua Bloomekatz helped me develop the ability to reason scientifically and appreciate the opportunities to grow professionally. I learned from him how to design experiments to answer important scientific questions. We often had lengthy discussions about the direction of my project. He helped me make sense of the collection of observations coming from different sources and nurtured my own independent thinking.In gaining an appreciation for his analytical method of thinking, I began to see myself as someday contributing to scientific thinking as a physician-scientist.

During your training at NIH, you worked on a project to find new treatments using zebrafish. What did you find exciting and challenging about studying zebrafish?

Most people are familiar with mice, which are often used in science to find and test new drugs. Working with mice requires a lot of work to have enough animals needed for an experiment. Zebrafish, on the other hand, can produce hundreds of offspring after one breeding cycle. Zebrafish lay eggs directly into water, which also makes it easier to study them soon after they hatch. Somewhat surprisingly,the zebrafish enzymes that handle propionic acid are very similar to the enzymes in humans. These two properties of zebrafish make them an exciting model to study a disease like propionic acidemia.

One of the most challenging parts of my research in zebrafish was their size. Zebrafish offspring are very small, measuring less than a quarter of an inch. I had to spend a lot of time looking at zebrafish under the microscope and learn how to move them around without hurting them. This can be difficult as these small animals are fragile at this young age.

Can you tell us about your PA project?

Earlier in my work, we were able to get zebrafish, which had mutations in the genes linked to propionic acidemia. I needed to understand what propionic acidemia does to zebrafish. We were able to show that propionic acidemia in zebrafish looks a lot like the disease we see in patients. Fish with propionic acidemia had poor appetite, did not grow well, and had difficulty moving. Using special genetic tools, we then attempted to change how zebrafish processed propionic acid and helped them survive longer. Our preliminary results are proving promising, but more work is still needed.

What are your plans after you complete your training at NIH?

The NIH postbac program is a full-time research award for students that have recently completed a bachelor’s degree and are considering a career in science or medicine. I was fortunate enough to join Dr. Charles Venditti’s lab 2 years ago to work on the zebrafish project under Dr. Oleg Shchelochkov. I thoroughly enjoyed my post-bac experience. Looking back on the past 2 years, I feel the lab, and in particular the mentorship of Dr. Shchelochkov, has facilitated and nurtured my growth as a future physician-scientist with roots in propionic acidemia research. In 2019 I applied to MD/PhD programs at several US universities. After having traveled to over half a dozen states and interviewing at many fantastic universities, I ultimately decided upon the physician-scientist training program at University of Minnesota. As I plan my transition to the program, I am currently looking for winter coats.

 

Liver Transplantation for Propionic Acidemia: FAQ

Liver Transplantation for Propionic Acidemia:

Part 1 – Answers to Questions that Families May Have

James Squires, MD, MS

Dr. James Squires

Dr. Squires is a liver disease specialist at Children’s Hospital of Pittsburgh of UPMC and an assistant professor of pediatrics at the University of Pittsburgh School of Medicine.

Jodie M. Vento, MGC, LCGC

Jodie Vento is a genetic counselor and manager of the Center for Rare Disease Therapy at the Children’s Hospital of Pittsburgh of UPMC.

What can we expect that a liver transplant could do for our child?

Based on experience to date with liver transplants in children with Propionic Acidemia (PA),we can say that after a liver transplant,children are likely to have a substantially better quality of life and a dramatic reduction in metabolic crises. It’s important for families to understand, however, that liver transplantation is not a cure for PA. This is because the enzyme deficiency that causes PA exists throughout the body, not just in the liver.

The liver transplant serves as what we liver specialists call a bulk enzyme replacement, providing enough functional enzyme to minimize – if not eliminate –metabolic crises, which are the most severe complications of PA for affected children as well as one of the most frightening features of the disease for families.

Because complications related to PA may still occur following a transplant, there will be a continued need for your child to get follow-up care with one or more medical specialists.

 

Is there a minimum or “best” age for a child with PA to have a liver transplant?

There is no minimum or “best” age. At our center, the average age of a liver transplant for a child with PA is about seven years old, but we have performed transplants in children as young as one year old.

The best time to consider a liver transplant is while the symptoms of PA are still reasonably well controlled. There is also no minimum age for undergoing a pre-transplant evaluation or being placed on the transplant waiting list.

What should we consider when deciding where to take our child for a liver transplant evaluation?

The most important factor to consider is the experience of the surgical team performing liver transplants in patients with PA and other metabolic diseases. These patients have complex needs that are different from those of patients receiving liver transplants for other conditions.

The pediatric liver transplantation program at Children’s Hospital of Pittsburgh of UPMC was established in 1981 by world-renowned transplant surgeon Thomas E. Starzl, MD, PhD. Our t Director of Pediatric Transplantation, George Mazariegos, MD, FACS, pioneered liver transplantation for children with metabolic diseases in 2004. Since that time, Children’s Hospital has performed more than 330 liver transplants for children with metabolic disease,more than any other transplant center.

We’ve also performed more liver transplants in children than any other center in the United States and more living-donor transplants than any other pediatric center in the country. Our one-year survival rate for pediatric liver transplant patients is 98%, exceeding the national average of 95%, according to the Scientific Registry of Transplant Recipients, Jan. 2018 release.

In addition to our world-renowned and experienced liver transplant surgeons, our Center for Rare Disease Therapy includes international experts in the diagnosis and treatment of PA and other metabolic diseases.

How would we start the process of having our child evaluated for a liver transplant?

I can tell you how the process works here at Children’s Hospital of Pittsburgh of UPMC. It starts with a referral from your doctor or hospital requesting that we evaluate your child. We also receive self-referrals directly from interested families. We will ask the doctor or hospital, or both, to send us all of your child’s medical records.

We will look at the records carefully to help us understand your child’s medical history and current situation. This information helps our multidisciplinary team develop an individualized plan for your child’s evaluation visit. For example, if your child has recently had certain laboratory or imaging tests done, we won’t repeat those tests unless there’s a valid medical reason for doing so. Understanding how the disease is affecting your child helps us identify which specialists your child should see during the evaluation.

It’s important for families to know that undergoing a pre-transplant evaluation involves no commitment on either side. It carries no guarantee that your child will be listed for a transplant or, conversely, any requirement that you must agree to have your child placed on the transplant waiting list. We can answer questions, provide information, and make recommendations. Ultimately, however, the decision to proceed with a transplant, or not, is a personal one for each family to make.

The evaluation is an opportunity for the family and the health care team to meet and get to know each other, as well as for the family to gather information and get answers to any and all questions you may have. We hope you’ll feel comfortable raising any concerns. Please don’t hesitate to ask us about any issue that’s on your mind. There are no dumb or silly questions. And, of course, if after you’ve gone home you think of something that you wish you had asked, please give us a call.

You can expect that the evaluation will be a two- or three-day event. The staff of our Center for Rare Disease Therapy will work with you to arrange for you, your child, and other family members to stay near the hospital, either at our Ronald McDonald house or at a nearby hotel, while you’re here for the evaluation.

We’ll send you a schedule in advance of your visit. This will tell you which medical and surgical specialists you’ll be seeing at what times and what laboratory or imaging tests we would like your child to have during the evaluation. To the extent possible, we try to anticipate all the testing we’ll need so that it’s a relatively smooth process while you’re here.

Please tell us more about what we can expect during our child’s evaluation.

Because PA is a genetic disease, the specialists you’ll see will likely include a medical geneticist and a metabolic dietician. Also, because PA often causes heart problems, your child’s evaluation is likely to include basic heart function tests and an assessment by a cardiologist. Depending on how the disease is affecting your child, the evaluation may also include visits with specialists such as the following:

  •         A neurologist, to assess brain function
  •         A gastroenterologist, to assess pancreas function
  •         A hematologist, to assess bone marrow function

Although we try to anticipate all the testing we’ll need and schedule it in advance, sometimes we may decide that it would be helpful to do an additional test that wasn’t originally on the schedule. For example, depending on the results of the basic heart function tests, the cardiologist might want to do a “stress test” that will provide more detailed information and measurements relating to how well your child’s heart is functioning.

 

If we decide to go ahead with listing our child for a transplant, what are our options for obtaining a donor liver? How long can we expect it to take to find a compatible donor?

PA is considered a high-priority condition for liver transplantation, so your child’s name will be near the top of the waiting list. However, because demand for donor livers is high and supply is limited, I tell families to be prepared to be on the waiting list for several months.

With any liver transplant, careful testing needs to be done to ensure compatibility of the donor liver and the transplant recipient.Many factors can influence the waiting time for a compatible organ. For example, a child with an uncommon blood type may face a longer wait.

In general, child-size donor livers are scarce. A unique feature of the liver, however, is that it is the only organ in the human body that can regrow. This means that in some cases it’s possible to transplant a section of a healthy liver rather than the whole organ. For example, a child who needs a liver transplant may receive a section of a liver from an adult donor. You may hear this type of transplant referred to as a “reduced-size” or “split” liver transplant.

Another type of liver transplant involves a living person – such as a relative, friend, or even a stranger – donating a section of their liver to someone who needs a transplant. Living-donor transplants may be an option for some children with PA. However, because PA is a genetic disease, parents and possibly siblings may be carriers of one of the genetic defects that cause the disease. Someone who is a carrier would not be a suitable living donor.

The good news is that children who receive a partial liver seem to do just as well as those who receive a whole liver. All of the options for obtaining a donor liver, including a reduced-size, split, or living-donor transplant, are discussed during the pre-transplant evaluation.

We’ve decided that a liver transplant is right for our child. What are the next steps?

When your child’s name is placed on the liver transplant waiting list, we will give you a pager that you will need to take with you everywhere you go so that we can reach you right away when we get a call that a matching donor liver is available. We don’t know when that call will come, but when it does you’ll need to be able to get to Children’s Hospital in a safe, but timely fashion. The transplant team will work with you to establish a ‘travel plan’ for you and your family for when the transplant is likely to occur.

While your child is on the waiting list, our specialists will work with your local doctors to care for your child and optimize their medical condition ahead of the transplant.

We know that waiting can be a difficult time for families. Your transplant coordinator is always available to respond to your questions and concerns and can also help you make travel arrangements.

Once you arrive at the hospital, preparations for the transplant may take from 12 to 24 hours. Your child will undergo another round of tests to confirm that the donor liver is a good match. Your child will also need to fast before surgery. Our metabolic dieticians will help us prepare intravenous fluids to provide your child with an individualized balance of fats, protein, and glucose to maintain stability while they can’t take anything by mouth.

The liver transplantation surgery may take up to several hours, although this varies in each case. While your child is in the operating room, a member of the transplant team will keep you informed on the progress of the transplant.

After the surgery, your child will go to the intensive care unit to be monitored closely until their condition is stable. Then your child will be moved to the liver transplant unit. Staff here will help you learn about your child’s medications, diet, need for follow-up care, and anything else you’ll need to know to care for your child.

After the transplant, will our child have to take anti-rejection medication?

After a liver transplant, you should expect that your child will need to take medication for the rest of his or her life to prevent organ rejection. The body’s normal reaction to a transplanted organ is to recognize it as a “foreign agent” and mount an immune response against the new liver. Anti-rejection medications suppress the immune system, which is the body’s defense system against illness and infection, to prevent it from attacking the new liver.

Because anti-rejection medications weaken the immune system, your child may be more likely to get infections – and those infections will be harder to treat. You will need to notify the transplant team at the first sign of an infection, such as a fever, chills, sweats, coughing, nasal congestion, diarrhea, redness or swelling, pain, or vomiting. A referral to a doctor may be needed as well.

With immune-suppressing medications, the goal is to find a treatment plan that achieves the needed degree of immune suppression while causing the fewest and least harmful side effects. Regular blood tests will help your child’s doctors monitor the medications’ effectiveness.

The risk of organ rejection declines over time. This means that in time your child should be able to take lower doses of anti-rejection medications. Most likely, however, he or she will need to continue taking at least a low dose of immune-suppressing medication lifelong.

Here at Children’s Hospital of Pittsburgh of UPMC and elsewhere, research is underway to learn more about whether some liver transplants patients can eventually stop taking immune-suppressing medication without increasing their risk for rejection of the transplanted organ. This research is a long-term effort, however, and it will be years before we can answer this question.

For more information, please visit: www.chp.edu/rarecare or call (412) 692-RARE (7273)

In Part 2 of this article, Dr. Squires will summarize the findings of a recent study of outcomes in children with PA and methylmalonic acidemia who received liver transplants at Children’s Hospital of Pittsburgh of UPMC.

Partners in Progress: Families and Scientists Catalyze Research for Rare Diseases

“Partners in Progress:  Families and Scientists Catalyze Research for Rare Diseases”

On Nov. 15, 2017, Baylor College of Medicine and Texas Children’s Hospital hosted a panel discussion as part of theEvenings with Genetics seminar series held at the Children’s Museum of Houston. The topic was “Partners in Progress:  Families and Scientists Catalyze Research for Rare Diseases” and panelists traveled from both coasts and the center of the country. Panelists included Jill Chertow Franks, President, Propionic Acidemia Foundation; Cynthia Le Mons, Executive Director of the National Urea Cycle Disorder Foundation, Tracy Smith Hart, Chief Executive Officer, Osteogenesis Imperfecta Foundation and Brendan Lee, MD, PhD, Robert and Janice McNair Endowed Chair, Professor, Department of Molecular and Human Genetics, Baylor College of Medicine. These family/scientist partnerships are a new and exciting development in the research efforts for those impacted by rare diseases.

The audience of almost 80 people consisted of parent leaders, rare disease foundations, medical students, genetic counseling students, pharmaceutical companies and undergraduate biotech majors. Each panelist discussed the partnerships with rare disease organizations and scientists and their strategies for success in obtaining funding for research from the National Institutes of Health (NIH). In addition, panelists shared how they became involved in the rare disease organization and offered advice for other rare disease organizations as well as researchers with regards to working together to submit requests for funding. Dr. Brendan Lee discussed the positive impact of family/scientist partnerships and that these collaborations highly beneficial for progress in understanding rare disorders and developing effective therapies.

Susan D. Fernbach, RN, BSN

Director of Genetic Outreach

Director of Diversity and Community Engagement

Assistant Professor, Dept. Molecular and Human Genetics

Baylor College of Medicine/Texas Children’s Hospital

Liver Transplant

Liver Transplant

There are many publications on liver transplantation for your review. The decision for families to have a liver transplant is a difficult one and is best discussed with your medical providers.

Family Experiences with Liver Transplants